1. Field of the Invention
This invention pertains to fabric stretching devices which provide clear access to stretched fabric while holding the fabric taut, enabling efficient needlepoint work to be performed upon the fabric.
2. Description of the Related Art
Heretofore, needlepoint stretchers have provided either a rigid, non--adjustable frame, or an adjustable frame at the sacrifice of rigid construction. Known to the inventor is a commercially available fabric stretcher for which no specific reference or documentation as prior art exists. This device utilizes two parallel upright arms and two rods which pass horizontally through the upright arm ends in a perpendicular fashion. Fabric is then wrapped around and stretched between the horizontal rods. The aforementioned design is commonly referred to as a "scroll stretcher", and this basic concept is utilized in U.S. Pat. No. 4,471,542 to Donald J. Unbenhauer (1984) and U.S. Pat. No. 3,098,280 to Harris Et Al (1963). Both of these aforementioned inventions modify the basic scroll stretcher design by using clamps which are integrated into the upright parallel arms, serving to stretch the fabric in a horizontal direction while fabric tension between the two scrolling rods maintains vertical tension. In studying these types of designs, however, the inventor has found that horizontal stretching of the fabric is necessary only because the rigidity of the frame is reduced whenever the rod clamps (thumb screws, in both cases) are loosened in order to turn the scrolling rods, an operation necessary in order to transport a new section of fabric into the work area as defined by the distance between the two scrolling rods. When frame rigidity is compromised, torsion caused by lack of rigidity between the upright parallel arms and the horizontal rods causes the frame to twist, resulting in diagonal ripples or lateral sags in the fabric. Thus, the two previously cited inventions compensate for their non-rigid, overly flexible frames by clamping the sides of the fabric and stretching the fabric transversely.
Also inherent in the design of previously cited scroll frame inventions (Umbenhauer and Harris Et Al), is a necessarily close tolerance between the horizontal rods and the holes in the upright frame members through which these rods pass. This tight fit is necessary because rod clamps must bend the upright arms, reducing the size of the holes through which the scroll rods pass in order to immobilize the rods and provide relative frame rigidity with minimum user effort. As the previously cited inventions are dependent on tight scroll rod compression for provision of a rigid frame, the scroll rods must be fitted in tight holes, resulting in friction between the upright arms and the horizontal rods. This friction results in difficulty of scroll rod adjustment.
Previously cited scroll type fabric stretchers (Umbenhauer and Harris Et Al) provide no capability for adjustment of the distance between the scroll rods. This capability is desirable because it enables the work area to be reduced to allow shorter fabrics to be mounted within the work area between the scroll rods.
Another crucial factor to be considered in scroll-type fabric stretchers is the manner in which the fabric is attached to the horizontal rods. Unbenhauer shows an ordinary, unaltered rod for fabric attachment, necessitating the use of adhesive tape or some other method in order to secure the fabric to the scrolling rod. Use of such tape may discolor, unravel, tear, or otherwise damage the fabric upon removal from the rod. The tape may also lose adhesion to either the fabric or rod during use, inconveniencing the user who must then re-fasten the fabric to the rod. In the previously mentioned invention by Harris Et Al, an exceptionally complex fabric holding rod is specified, utilizing over twenty parts in the rod assembly alone. This complexity, while possibly effective, virtually eliminates the invention from the competitive marketplace due to exceptionally high manufacturing costs.
Other stretcher designs, such as U.S. Pat. No. 800,591 to C. Payen (1905), provide a rigid frame on which fabric can be uniformly stretched, however the maximum fabric size is limited to the size of the frame itself.